This research project is concerned with experimental study of hemodynamic and associated physiological responses of laboratory dogs trained on operant conditioning tasks which require them to elevate total peripheral resistance in order to avoid the onset of aversive stimuli. Short-term experiments will investigate concurrent effects of these conditioning procedures upon arterial pressure, cardiac output, heart rate and stroke volume, using chronically implanted cardiovascular sensors and a computerized system for data recording and reduction. In addition, the role of the autonomic effector system and the baroreceptor reflex in the mediation of this cardiovascular response will be investigated. Long-term experiments will be conducted to determine effects upon blood pressure of repeated exposure to environmental contingencies which elicit acute elevations in total peripheral resistance.